Overview
If the Chinese mitten crab invaded New Zealand waters it could pose a serious threat to both our marine biological communities and the stability of our river banks. This crab is native to the rivers and estuaries of China and Korea along the Yellow Sea. The young crabs grow and develop in freshwater.

When adults, they migrate to the sea to reproduce and die. They burrow into river banks and can cause accelerated erosion and slumping. They have also been known to block water intakes in irrigation and water supply schemes. They carry a lung fluke that infects humans.

Mode of distribution
Chinese mitten crabs could arrive in New Zealand as young animals in a ship's ballast water or as adults in a vessel's seachests.

It is also a food source in some cultures and so could be introduced deliberately.

Description
Size: Adult up to 80 mm wide, juvenile up to 20-25 mm wide.
Colour: Light brown.
Body shape: Smooth and rounded.

Key features
The front claws of the crabs that are 25 mm or wider are hairy with white tips.

Their legs are twice as long as the width of their body and they have a notch between the eyes.

Action plan
Chinese mitten crab action plan September 2001 (PDF 356KB).

(You'll need Adobe Acrobat Reader to read the PDF files; it's available to download for free. It may take a while to download.)